There is evidence that the overall health of the River Murray system is in decline.

The pressure on the River Murray system includes changed flow regimes, salinity, cold-water pollution, turbidity, removal of snags, riverbank erosion, over-grazing of floodplains, the spread of exotic species, and over-fishing in some areas.

In April 2002, the Murray-Darling Basin Ministerial Council called for social, economic and ecological assessments of the costs and benefits of returning additional water to the River Murray as environmental flows. The MDBC Ministerial Council chose three flow volumes – 350, 750 and 1500 GL per year – as 'reference points' for assessment (one gigalitre (GL) is equivalent to 1000 million litres).

The MDBC contracted the Cooperative Research Centre for Freshwater Ecology to assemble a Scientific Reference Panel (SRP) to undertake the ecological assessment.

The Council later directed that the focus for assessment be on achieving outcomes at six significant ecological assets. Please refer to the First Step Decision for more information.

Assessment process

To inform the assessment of the Scientific Reference Panel, ten Regional Evaluation Groups (REGs) were set up. Each REG assessed a specific zone along the River Murray system, and also the Murrumbidgee River. Each REG comprised 4–8 experts with local and regional ecological and river management knowledge. The river zone assessments by the REGs were subsequently used as a basis for the system-wide assessment of the River Murray by the SRP.

The MFAT was used in the assessment to ensure a consistent approach across the river zones.

Daily river flows for the past 108 years (1891–1999) modelled using MSM-Bigmod were used as the input to MFAT for River Murray zones. A different river hydrology model called IQQM was used to generate flow scenarios for the Murrumbidgee River.

Flow Scenarios Used
Three alternative flow scenarios ('cap', 'b' and 'c') for each volume (350, 750 and 1500 GL) were used as input to MFAT for River Murray zones;

• 'Cap' scenarios

This is where in the model the Cap was reduced on the Murray, Lower Darling, and tributaries. Then as the reservoirs became full, they were allowed to spill over thus releasing environmental flows.

• 'b' scenarios

This is where in the model environmental flows were released from reservoirs and managed to target key localities in the Murray e.g. the Mitta Mitta River, wetlands downstream of Hume, Barmah-Millewa Forest and the Murray Mouth.

• 'c' scenarios

This is where in the model environmental flows were released from reservoirs, and managed to target key localities in the Lower Darling as well as the localities in the 'b' scenario.

In MFAT 'Natural', 'current' and 'reference' scenarios were also assessed for comparison:

• The natural scenario is the flow conditions without flow regulation or diversion
• The 'Current' scenario is the flow conditions under levels of development that existed in 2002 - land use, regulation and diversions
• The 'Reference' scenario is the flow condition as at the 93/94 Cap, which represents the limit placed on the volume of water that can be diverted from the Basin's rivers for consumption. Further information on the Cap is available from http://www.mdbc.gov.au/naturalresources/the_cap/the_cap.htm.

You can find more details on the flow scenarios that were used in the SRP assessment in Appendix three of the Interim Scientific Reference Panel (SRP) Report, October 2003 [PDF 1.0 MB].

The flow scenarios assessed using MFAT for the Murrumbidgee River (a major tributary of the River Murray) are different from those produced for the River Murray and were generated using a model called IQQM. Scenarios assessed were; 'Natural', 'Reference', 'Current', 'Year 6 Water Sharing Plan (WSP)', '10%' and '20%' reduction of Current. The latter three scenarios are approximately equivalent to the 350, 750 and 1500 GL scenarios assessed in River Murray zones. You can find more details on the flow scenarios that were used in the Murrumbidgee River assessment in the Zone J Regional Evaluation Group Report [PDF 863.2 KB].

More information on the assessment process is available in the Interim Scientific Reference Panel (SRP) Report, October 2003 [PDF 1.0 MB].

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Use of MFAT in the future

The Murray-Darling Basin Commission plans to further invest in the development of MFAT during 2004/05 to enhance the model within its existing framework.

This process will take on board feedback received from scientists who have participated in the development, application and review of MFAT.

The MFAT can be used in combination with hydrological and other models to help inform the development of environmental watering plans for the SEAs and the River Murray system to achieve the ecological objectives of the Living Murray First Step Decision.

For more information please Contact Us.

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